Udder diseases of diary cows

Abstract

T IlE DAIRY cow'S udder (fig. 1) has been highly developed by cen turies of careful, selective breeding. It is complex in its structure and physiology. The secretory tissue of the gland is made up of great numbers of alveoli or hollow balls composed of milk-secreting cells which are mi croscopic in size and grouped like clusters of grapes around the ducts (fig. 2). The milk is formed in the alveoli and travels down through the ducts to the gland cistern and teats. The size of the passageway through the teat is greatly reduced at its lower end. This constriction prevents escape of milk from the udder and acts as a barrier against entrance of micro-organisms. Each quarter of the udder is separate and milk is being continually secreted in active glands. Much of it, however, is only forced down.